Build optimized LLVM/Clang compiler.

Change-Id: Ie03b313d7f6ca89c73dee6361385d27216780fe6
diff --git a/build/tools/build-llvm.sh b/build/tools/build-llvm.sh
index 0dd8dbb..a42e594 100755
--- a/build/tools/build-llvm.sh
+++ b/build/tools/build-llvm.sh
@@ -127,6 +127,7 @@
     --build=$ABI_CONFIGURE_BUILD \
     --with-bug-report-url=$DEFAULT_ISSUE_TRACKER_URL \
     --enable-targets=arm,mips,x86 \
+    --enable-optimized \
     $CONFIG_FLAGS
 fail_panic "Couldn't configure llvm toolchain"